1. Field of the Invention
This invention relates to methods and devices for controlling the operation of the human heart or other organs by means of electrical stimulation, and more particularly, to devices for electronically slowing or stopping the heart.
2. Description of the Related Art
In some surgical procedures, such as coronary bypass surgery, it is necessary to stop the heart from beating so that the surgeon can perform necessary techniques. The use of a cardioplegia solution to stop the heart from beating without rerouting the blood would permit the surgeon to accomplish the required task without interference from heart movement. However, this is not a viable approach, since the body needs a constant supply of oxygen. Thus, there exists a need to temporarily slow down or stop heart movement during minimally invasive CABG or other surgical procedures to permit the surgeon to accomplish the required task. In the context of treatment of the heart by means of implanted medical devices, such as pacemakers, defibrillators and drug dispensers, it is also sometimes beneficial to slow or temporarily stop the heart, either for diagnostic or therapeutic purposes.
It has been known in the past to stimulate the vagal nerves by invasively dissecting the major nerve bundle and placing a spiral or enveloping nerve-type cuff around the nerve bundle. The nerve fibers are then directly stimulated by electrical field to achieve reduction in epilepsy, heart rate slowing, and potential blood pressure changes. In a study entitled xe2x80x9cSelective Stimulation of Parasympathetic Nerve Fibers to the Human Sinoatrial Nodexe2x80x9d, Circulation, Vol. 85, No. 4, April 1992, it was reported that cardiac parasympathetic nerve fibers located in an epicardial fat pad at the margin of the right atrium, the superior vena cava, and the right pulmonary vein in humans could be electrically stimulated to affect the heart rate. Additional reference is found in PACE October 1992 Vol. 15, No. 10, pt. 11, pages 1543-1630 on the use of nerve cuff stimulation of the vagal nerves (left side) in humans for reduction of epilepsy and it""s side-effects. Additional uses for electrical nerve stimulation have been disclosed for the prevention of arrhythmias, alteration of hemodynamics, stimulation of the hypoglossal nerve for sleep apnea, stimulation of the stomach, and control of the sphincter for bladder or colon evacuation.
Currently, only nerve cuff-type electrodes or impalement-type electrodes are used for nerve stimulation, other than in the spinal cord. These types of electrodes can potentially cause irreversible nerve damage due to swelling or direct mechanical damage of the nerve. The placement of these electrodes either around the nerve bundle or into the neural perineum also poses a significant risk. The electrode placement is usually performed through very invasive surgery which in and of itself produces a high risk to nerve damage, and would be self-defeating when performing minimally invasive surgery. However, it has been demonstrated that the paraympathetic nerve fibers associated with the heart can also be stimulated by means of electrodes located on transvenous leads, as in U.S. Pat. No. 5,243,980, issued to Mehra et al, U.S. Pat. No. 5,507,784, issued to Hill et al and U.S. Pat. No. 5,356,425, issued to Bardy et al. The use of transvenous electrode leads to stimulate parasympathetic nerves associated with the heart is also discussed in the article xe2x80x9cNeural effects on Sinus Rate and Atrial Ventricular Conduction Produced by Electrical Stimulation From a Transvenous Electrode Catheter in the Canine Right Pulmonary Arteryxe2x80x9d, by Cooper et al., published in Circulation research, Vol. 46, No. 1, January 1980, pp. 48-57.
In conjunction with spinal cord stimulation, electrodes or electrode arrays located on pliant electrode pads are often employed. Recently, the ability to select from among various pairs of electrodes located on such electrode pads has been proposed to allow steering of the electrical field produced by the electrodes, as in U.S. Pat. No. 5,501,703, issued to Holsheimer, incorporated herein by reference in its entirety. Such electrode arrays offer additional possibilities to stimulate nerve fibers without direct and possibly damaging contact.
It is with these problems in mind that a new apparatus and method have been developed for electrically stimulating or destimulating certain nerves associated with the functioning of the heart or other organs which can be combined with certain surgical procedures or incorporated into implantable medical devices. According to one aspect of the invention, the invention is embodied in an electro-stimulation device includes at least two electrodes for connection to at least one location in the body that affects or regulates the heartbeat. At least one switch is connected between a power supply and the electrodes for selectively supplying current from the power supply to the electrodes to augment the natural stimuli to the heart in order to control the beating of the heart, and preferably to stop the heart from beating. Preferably, the switch is a foot switch operable by a surgeon to free a surgeon""s hands during surgery.
According to another aspect of the invention, the at least two electrodes are connected to an intravenous catheter for transvenous stimulation/destimulation of the heartbeat.
According to another feature of the invention, an electro-stimulation device for both electrically destimulating and stimulating the heart includes a pair of electrodes for connection to at least one location in the body that affects or regulates the heartbeat. A first switch is connected between a power supply and the electrodes for selectively supplying current from the power supply to the electrodes to augment the natural stimuli to the heart and thereby stop the heart from beating. A second switch is connected between the power supply and the electrodes for selectively supplying current from the power supply to the electrodes to provide an artificial stimulus to initiate the heartbeat.
In a further aspect of the invention, a method for arresting the beat of a heart in a living body includes the process of connecting a pair of electrodes to at least one location in the body that affects or regulates the heartbeat and supplying an electrical current to the electrodes of sufficient amplitude and duration to arrest the heartbeat. According to one aspect of the invention, the step of supplying an electrical current to the electrodes includes supplying an alternating current.
In yet further aspects of the invention, the invention is embodied in an external or implantable device which employs electrodes located on transvenous leads located in veins adjacent nerve fibers to be stimulated in these aspects of the invention, the leads preferably carry an array of electrodes from which pairs of electrodes can be chosen in order to direct the electrical field appropriately with respect to the desired nerve fibers.
It is to be noted that with regard to the effect of the delivered nerve or other stimulus pulses relative to the action of the heart the phrase xe2x80x9cstimulate the heartxe2x80x9d and its derivatives as used herein refer to the initiation of the heartbeat through the application of electricity, while the phrase xe2x80x9cdestimulate the heartxe2x80x9d and its derivatives refer to stopping or arresting the heartbeat through the application of electricity.